Field of the Disclosure
The technology of the disclosure relates to distributed communication systems, and in particular to providing devices, systems, and methods to allow determination of the location of client devices within distributed communication systems.
Technical Background
Wireless communication is rapidly growing, with ever-increasing demands for high-speed mobile data communication. “Wireless fidelity” or “WiFi” systems and wireless local area networks (WLANs) are now deployed in many different types of areas. Distributed antenna systems communicate with wireless devices called “clients,” “client devices,” or “wireless client devices,” which must reside within the wireless range or “cell coverage area,” to communicate with an access point device. Distributed antenna systems are particularly useful inside buildings or other indoor environments where client devices may not otherwise effectively receive radio frequency (RF) signals from a source.
Distributed antenna or distributed communication systems have RF antenna coverage areas, also referred to as “antenna coverage areas.” Antenna coverage areas can have a relatively short range—from a few meters up to twenty meters. Combining a number of access point devices creates an array of antenna coverage areas. Because the antenna coverage areas each cover small areas, there are typically only a few client devices per coverage area. This minimizes the amount of bandwidth shared among the wireless system users. Typical indoor distributed communication systems include a central or head-end unit communicatively coupled to a plurality of remote units that each provides an antenna coverage area. The remote units each include RF transceivers coupled to an antenna to transmit communication signals (e.g., RF, data) wirelessly. The remote units are coupled to the head-end station via communication media to receive downlink communication signals to be wirelessly transmitted over an antenna in the coverage area to client devices. The remote units also wirelessly receive uplink communication signals from client devices to be communicated to the head-end station.
FIG. 1 is a schematic diagram of an optical fiber-based distributed communication system 10. The system 10 is configured to create one or more antenna coverage areas for establishing communication with wireless client devices (sometimes referred to herein as mobile terminals) located in the RF range of the antenna coverage areas. The system 10 includes a central unit or head-end unit (HEU) 12, one or more remote antenna units (RAUs) 14 and an optical fiber link 16 that optically couples the HEU 12 to the RAU 14. The HEU 12 is configured to receive communication over downlink electrical RF signals 18D from a source or sources, such as a network or carrier, and provide such communication to the RAU 14. Such downlink communication signals are received through a conventional input, such as a downlink input. If multiple sources are present, there may be multiple downlink inputs. The HEU 12 is also configured to return communication received from the RAU 14, via uplink electrical RF signals 18U, back to the sources. The optical fiber link 16 includes at least one downlink optical fiber 16D to carry signals communicated from the HEU 12 to the RAU 14 and at least one uplink optical fiber 16U to carry signals communicated from the RAU 14 back to the HEU 12. An interface couples the HEU 12 to the optical fiber link 16. The interface may be a conventional interface configured to receive downlink communication signals and pass the downlink communication signals to the RAU 14 through the link 16.
The system 10 has an antenna coverage area 20 that can be substantially centered about the RAU 14. The antenna coverage area 20 of the RAU 14 forms an RF coverage area 22. The HEU 12 is adapted to perform any one of a number of Radio-over Fiber (RoF) applications, such as radio-frequency identification (RFID), WLAN communication, or cellular phone service. Shown within the antenna coverage area 20 is a client device 24 in the form of a mobile terminal as an example, which may be a cellular telephone, smart phone, tablet computer, or the like. The client device 24 can be any device that is capable of receiving RF communication signals. The client device 24 includes an antenna 26 (e.g., a bipole, monopole, bowtie, inverted F, a wireless card, or the like) adapted to receive and/or send electromagnetic RF signals.
The HEU 12 includes an electrical-to-optical (E/O) converter 28 to communicate the electrical RF signals over the downlink optical fiber 16D to the RAU 14, to in turn be communicated to the client device 24 in the antenna coverage area 20 formed by the RAU 14. The E/O converter 28 converts the downlink electrical RF signals 18D to downlink optical RF signals 30D to be communicated over the downlink optical fiber 16D. The RAU 14 includes an optical-to-electrical (O/E) converter 32 to convert received downlink optical RF signals 30D back to electrical signals to be communicated wirelessly through an antenna 34 of the RAU 14 to client devices 24 located in the antenna coverage area 20.
The antenna 34 receives wireless RF communication from client devices 24 and communicates electrical RF signals representing the wireless RF communication to an E/O converter 36 in the RAU 14. The E/O converter 36 converts the electrical RF signals into uplink optical RF signals 30U to be communicated over the uplink optical fiber 16U. An O/E converter 38 in the HEU 12 converts the uplink optical RF signals 30U into uplink electrical RF signals, which are then communicated as uplink electrical RF signals 18U back to a network.
As noted above, it may be desired to provide the distributed communication system 10 in FIG. 1 indoors, such as inside a building or other facility. Other services may be negatively affected or not possible due to the indoor environment. For example, it may be desired or required to provide localization services for the client devices 24, such as emergency 911 (E911) services. If a client device is located indoors, techniques such as global positioning services (GPS) may not be effective at providing or determining the location of the client device. Indoors, GPS signals are usually too weak to be received by client devices. Further, triangulation and/or trilateration techniques from the outside network may not be able to determine the location of client devices.
Other methods for determining location of client devices may be based on receiving wireless data signals transmitted by existing wireless data devices provided in wireless communication systems (e.g., cell phone network and/or WLAN access points). However, use of existing wireless data signals may only be accurate to down to a resolution of still a relatively large distance (e.g., ten meters) since the client devices may receive wireless data signals from wireless data devices not in close proximity to the client devices. Further, use of existing wireless data signals for localization may necessitate a greater density of RF communication devices than is required for data communication. Thus, determining location of client devices at lower resolution distances (e.g., less than ten (10) meters, floor level in a building, etc.) using wireless communication signals transmitted from existing wireless data devices may not be possible without providing additional, greater densities of these wireless data devices at greater cost and complexity.